Flow structure and heat transfer in a horizontal converging channel heatedfrom below

A detailed experimental study is carried out to investigate the flow struct ure and heat transfer in a converging horizontal channel with localized hea ting on the bottom surface. This configuration arises in typical chemical v apor deposition (CVD) systems and the impact of the transport mechanisms on the deposition process is of particular interest. Experimental observation s of various flow circumstances indicate the appearance of longitudinal and transverse roll structures. These flow structures have direct implications with respect to CVD processing where deposition rates and film quality are critically dependent on reactive species and byproduct transport onto the deposition surface. Different flow regimes are observed for typical operati ng conditions, and their existence is described using regime maps. Regime b oundaries are correlated in terms of important parameters that describe the flow rate, heating rate, and tilt angle. A regime transition from longitud inal rolls to transverse rolls occurs at around Gr/Re-2 = 6000, while the c ritical Rayleigh number is found to be dependent on the flow. Heat transfer correlations are also derived and it is seen that the heating rate is the dominant effect on the susceptor temperature, while the effects of flow rat e and tilt angle are small. The implication of heat transfer results on mas s transfer are discussed for horizontal CVD reactors. The flow structure an d heat transfer phenomena observed in this study yield valuable insight int o the basic buoyancy and forced-flow-induced transport in horizontal channe ls as well as guidelines for the modeling and design of CVD systems. (C) 20 00 American Institute of Physics. [S1070-6631(00)01907-3].